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光纤耦合器是全光纤傅里叶变换光谱仪(FFTS)的关键元件。根据耦合模理论,分析了光纤耦合器的分束比、附加损耗等传输特性对FFTS的工作带宽和测量准确性的影响。提出一种修正方法,即根据耦合模理论,拓展光纤耦合器传输矩阵的定义,通过实验测量确定其值,进一步计算得到反映光纤耦合器传输光谱特性的窗形函数,用于FFTS的光谱修正。采用此修正方法不但拓宽了FFTS的工作带宽,提高了其测量准确性,而且降低了FFTS对光纤耦合器传输特性的要求。
Fiber Couplers are a key element of all-fiber Fourier Transform Spectroscopy (FFTS). According to the coupling mode theory, the influence of transmission characteristics such as splitting ratio and additional loss on the working bandwidth and measurement accuracy of FFTS is analyzed. A correction method is proposed based on the coupled-mode theory. The definition of fiber coupler transmission matrix is extended. The value of the fiber-coupler coupling matrix is determined through experimental measurements. A window function reflecting the transmission spectral characteristics of the fiber coupler is calculated and used for spectral correction of FFTS. The adoption of this method not only broadens the working bandwidth of FFTS but also improves its measurement accuracy, and reduces the requirements of FFTS on the transmission characteristics of optical fiber coupler.